1. Field of the Invention
This invention relates to surgical filter masks.
2. The Prior Art
Filter masks have historically been used to reduce the dispersion of micro organisms from the respiratory system of medical personnel involved in procedures requiring aseptic conditions, for example, surgery. The filter mask also serves to minimize the inhalation of micro organisms originating from an external source, such as a patient. Originally, filter masks were made of a woven gauze or linen material which proved to be relatively comfortable to the wearer, however, which also proved to have a relatively low filtering efficiency.
A greater degree of filtering efficiency has been obtained through the recent development of non-woven filter masks. However, the air resistance of a filter medium is generally proportional to the filtering efficiency. With greater air resistance, the non-woven filter masks currently available tend to collapse about the nose and mouth of the wearer upon inhalation, particularly after a period of use when the filter medium has become dampened through the moisture in the exhalant of the wearer. This collapse about the nose and mouth of the wearer is not only uncomfortable and bothersome, it also reduces the filtering efficiency of the filter mask by forcing a greater volume of air through the smaller surface area of the collapsed mask.
Prior art attempts in providing a framework for supporting the filter medium away from the nose and mouth of the wearer have been disclosed, for example, see U.S. Pat. Nos. 1,319,273 and 2,149,067. These, however, are bulky and present packaging and storage difficulties.
A British Pat. No. 5104AD1913 discloses a filter mask wherein the filter medium is gathered upon pulling of a draw string so as to enclose the nose and mouth with the filter mask and incorporates a vertically extending braid to partially support the filter medium away from the nose and mouth of the wearer.
Size reductions have been achieved by pleating the filter medium, for example, as disclosed in U.S. Pat. No. 3,802,429. Pleating provides only very limited support and does not prevent the eventual collapse of the filter mask about the nose and mouth of the wearer during use.
It would therefore be an improvement in the art of filter masks to provide a filter mask foldable into relatively reduced dimensional and flat configuration for ease of packaging and shipment while also providing an enlarged filtering surface having an integral support therein. The support should hold the filtering medium away from the nose and mouth of the wearer when the filter mask is expanded into its operating configuration. Such an invention is disclosed herein.